Due to use of exhaust ventilation like kitchen hood or restroom's exhaust fan there is a normally negative pressure inside dwellings and other naturally ventilated facilities. If there is no mechanical fresh or supply air arrangement then, it indirectly means natural ventilation. Fresh air is arranged either by leakages in construction or by opening windows or by other openings to outdoors. This arrangement does not provide purification of fresh air, thus when outdoor is polluted simultaneously indoor pollutants level will increase, like PM2.5 levels. Temperature or humidity content of fresh air is hard to control and also the outdoor noises.
In naturally ventilated house the rooms are very airtight, carbon dioxide level can rise within few hours from few hundreds ppm to the level that is unhealthy or even harmful to humans. Thus opening of the window within several hours' frequency is needed or alternatively need to keep it open.
In some countries like China, especially in new buildings, there are several, ready to access holes (pipes through the walls) in construction phase for installing split type air conditioners. These pipes are usually located at non-reachable places like corners, thus known solutions are not suitable or existing fresh air system does not fit on available locations.
On the other hand making hole through wall is a normal practice, but size should be minimized, otherwise noise pollution from outside will increase unnecessarily. Big hole may also bring in too much hot or cold air this may cause high moisture and damage the walls, if open surfaces are not sealed properly. Alternatively temperature and humidity difference can cause dew point inside fresh air inlet causing together with organic dust potential risk for microbial growth. Fresh air from outdoor is needed mainly to dilute indoor pollutant levels.
Carbon dioxide level is often used as indicator for fresh air needs. The outdoor air in most locations contains about 300-400 ppm, carbon dioxide. Higher outdoor CO2 concentrations can be found near vehicle traffic areas, industry, and sources of combustion. Indoor air quality standards—like in China GB/T 18883-2002 has limit value of 1000 ppm. When indoor carbon dioxide concentration is elevated, (compared to the outside air) the source would be the building's occupants. Human exhale carbon dioxide, the average adult's exhale contains about 35,000 to 50,000 ppm of CO2 (100 times higher than outdoor air). CO2 can accumulate if there is no adequate ventilation to dilute and remove the CO2 i.e. continuously exhaled by the occupants. High CO2 level can also indicate high concentration of other chemical pollutants like CO, O3, Formaldehyde, B(a)P, TVOC, Polybrominated diphenyl ethers (PBDEs) or biological organisms like viruses, molds and bacteria's.
Carbon monoxide poisoning is the most common type of fatal air poisoning in many countries. Carbon monoxide is colorless, odorless, and tasteless, but highly toxic. In China, based on standard GB3095-2012, one hour average is 4 mg/m3 and daily average is 10 mg/m3. Within short time scales, carbon monoxide absorption is cumulative, since the half-life is about 5 hours in fresh air.
Polybrominated diphenyl ethers (PBDEs) causes delayed mental and physical development, lower IQ, advanced puberty and reduced fertility. Other flame retardants have been linked to cancer. They have been applied to textiles, foam in couches and baby products, building insulation, carpets, drapes, personal computers, TV sets, car dashboards, electrical cables and many other products. Because they are not chemically bound to material but incorporated during manufacturing or sprayed on afterward, they routinely escape as vapor or airborne particles that tend to stick to surfaces or settle in dust.
Formaldehyde's sources and pathways of exposure indoor sources may be combustion processes such as smoking, heating cooking, or candle or incense burning. However, major sources in non-smoking environments appear to be building materials and consumer products that emit formaldehyde. The average outdoor formaldehyde concentration in selected Chinese was 11.7 μg/m3 for the period of 1997-2006 is disclosed in X. Tang el./ Environment International 35 (2009) 1210-1224. In China Indoor Air Quality Standards—GB/T 18883-2002 limit value for formaldehyde is 100 μg/m3.
“WHO Air Quality Guidelines” based on recent conclusive associations between daily mortality and lower ozone concentrations has recommended air quality limit in their 2005 Air Quality Guidelines for Ozone (O3) edition and the said limit is 100 μg/m3 8-hour mean. Excessive ozone in air can cause a marked effect on human health. It may lead to breathing problems, trigger asthma, reduce lung function and cause lung diseases. In Europe it is currently one of the air pollutants of most concern. Several European studies have reported that the daily mortality rises by 0.3% and that for heart diseases by 0.4%, per 10 μg/m3 increase in ozone exposure.
The current WHO guideline value of 40 μg/m3 (annual mean) was set to protect the public from the health effects of Nitrogen dioxide gas. As an air pollutant, NO2 has several correlated activities, with short-term duration its concentrations exceeds 200 μg/m3, it is a toxic gas which causes significant inflammation of the airways. NO2 is the main source of nitrate aerosols, which form an important fraction of PM2.5 and, in the presence of ultraviolet light, of ozone. NO2 is present in motor vehicle exhaust as well as in fumes from kerosene and other non-electric heaters, gas stoves and clothes dryers, fireplaces, and tobacco. It's also found in emissions from power plants and industrial boilers.
Sulfur dioxide (SO2) has guideline values of 20 μg/m3 24-hour mean, 500 μg/m3 10-minute mean. A SO2 concentration of 500 μg/m3 should not be exceeded over average periods of 10 minutes duration. Studies indicate that a proportion of people with asthma experience changes in pulmonary function and respiratory symptoms after periods of exposure to SO2 as short, as 10 minutes. SO2 can affect the respiratory system and the functions of the lungs, and causes irritation of the eyes. Inflammation of the respiratory tract causes coughing, mucus secretion, aggravation of asthma and chronic bronchitis and makes people more prone to infections of the respiratory tract. Hospital admissions for cardiac disease and mortality increase on days with higher SO2 levels. Three studies measured outdoor levels in urban and rural areas of the same country as referred in Spengler at al., 1979; Lee at al., 1999; Kendzierski and Sembaluk, 2001. All found that more densely populated urban areas had higher outdoor SO2 levels. Industrial, home heating and vehicular traffic emissions are potential sources related to population density.
Volatile organic compounds—VOCs are a well-known outdoor air pollutant. They are categorized as either methane (CH4) or non-methane (NMVOCs). Methane is an extremely efficient greenhouse gas which contributes to enhance global warming. Other hydrocarbon VOCs are also significant greenhouse gases because of their role in creating ozone and prolonging the life of methane in the atmosphere. This effect varies depending on local air quality. The aromatic NMVOCs benzene, toluene and xylene are suspected carcinogens and may lead to leukemia with prolonged exposure.
Particulate matter (PM) affects more people than any other pollutant. The major components of PM are sulfate, nitrates, ammonia, sodium chloride, black carbon, mineral dust and water. It consists of a complex mixture of solid and liquid particles of organic and inorganic substances suspended in the air. The most health-damaging particles are those with a diameter of 10 microns or less, (≤PM10), which can penetrate and lodge deep inside the lungs. Chronic exposure to particles contributes to the risk of developing cardiovascular and respiratory diseases, as well as of lung cancer.
Air quality measurements are typically reported in terms of daily or annual mean concentrations of PM10 particles per cubic meter of air volume (m3). Routine air quality measurements typically describe such PM concentrations in terms of micrograms per cubic meter (μg/m3). When sufficiently sensitive measurement tools are available, concentrations of fine particles (PM2.5 or smaller), are also reported.
There is a close, quantitative relationship between exposure to high concentrations of small particulates (PM10 and PM2.5) and increased mortality or morbidity, both daily and over time. Conversely, when concentrations of small and fine particulates are reduced simultaneously mortality will also go down—presuming other factors remain the same. This allows policymakers to project the population health improvements that could be expected if particulate air pollution is reduced.
Small particulate pollution have health impacts even at very low concentrations—indeed no threshold has been identified below which no damage to health is observed. Therefore, the WHO 2005 guideline limits aimed to achieve the lowest concentrations of PM possible.
Noise pollution is recognized as a major problem for the quality of life in urban areas all over the world. Because of the increase in the number of cars and industrialization, noise pollution has also increased. Noise in cities, especially in main areas, has reached up disturbing levels. The complex urban soundscape is shaped by a combination of environmental noise from transit systems, road traffic, construction, industry, the built environment, population density and other sources.
The noise pollution is not a unique problem for developing countries only. Many researchers have revealed that, more than 130 million people in Europe suffer from exposure to noise levels above 65 dB (A). Bond M (1996) Plague by noise, New Scientist 16: 14-15, reports that 16% of people in Europe are expose to 40 dB(A) or more of traffic noise in their bed rooms at night compare it with WHO's average estimates of 30 to 35 dB(A) for undisrupted sleep. World Health Organization has announced that during nighttime outdoor sound level should not exceed 45 dB(A).
In addition to criteria affecting the degree of air cleanliness, factors such as cost (initial investment and maintenance), space requirements, and airflow resistance have led to the development of a wide variety of air cleaners. The three distinguishing operating characteristics are efficiency, resistance to airflow, and dust-holding capacity.
Minimum efficiency during the life of the filter is the most meaningful characteristic for most filters and applications. Resistance to airflow (or simply resistance) is the static pressure drop differential across the filter at a given face velocity. The term static pressure differential is interchangeable with pressure drop and resistance if the difference of height in the filtering system is negligible.
Dust-holding capacity defines the amount f a particular type of dust that an air cleaner can hold when it operates at a specified airflow rate to some maximum resistance value.
Complete evaluation of air cleaners therefore requires data on efficiency, resistance, dust-holding capacity, and the effect of dust loading on efficiency and resistance.
High-efficiency particulate air (HEPA) filter must remove at least 99.97% of all particles greater than 0.3 micrometer from the air that passes through it. EPA/HEPA/ULPA filter classification is based on values for local particle collection efficiencies (local values) and integral efficiency (integral value). Each is assessed on the basis of the most penetrating particle size (MPPS). Because of the features of the filter the pressure drop is high the usage for fresh air filtration is very limited.
Coarse, Medium and Fine filters are disposable air filters designed to operate through a specific performance rate and then discarded and replaced. Filtration efficiency of Coarse, Medium and Fine filters improves when dust loading increase. Simultaneously pressure drop also increase and filtration efficiency is the highest just before changing the filter. These types of filters are not efficient for small size of particles (like 0.4 micron) and usage for filtering re-circulated indoor air is limited.
Water and mist filtration has three serious disadvantages against other filters and those are: 1. control of the humidity and moisture nearby filter unit, 2. risks for bacterial growth (like legionella) as water is not changed periodically and 3. consumption of the water if water is used continuously.
Ozone generators are not suitable to be used as fresh air purposes: instead ozone is one of the main pollutants that need to be filter off from fresh air and re-circulated indoor air.
Photocatalytic oxidations (PCO) is inefficient for filtering fresh air from outdoor, for purifying re-circulated air it has some effects but there are also found as disadvantage that it may create formaldehyde and acetaldehyde, both hazardous for humans.
Ultraviolet germicidal irradiation (UVGI) technology is good for destroying DNA structures of microbes but it need enough time for radiate enough energy dosage. Therefore using it for sterilizing microbes from free flowing air is inefficient. UVGI technology is suitable for killing living organism inside filter unit that are either trap to filter media or inner surfaces of the casing.
Chemical filters are needed for removing gaseous contaminants from the air. Often used activated carbon is not efficient for filtering high vapor pressure gases, like formaldehyde. Depending on gaseous contaminant and dosages, chemical filters need certain composition and adsorption time, which is correlating with air speed through material. Even this requirement needed thickness of activated carbon granulates having high pressure drop when using traditional method of manufacture.
Most of the air purifiers on the market are having chemical filter with activated carbon granulates. They have installed granulates inside honeycomb type metal or plastic structure and covered it both side with stretchy net made from either metal or plastic. Disadvantage of this type of solution is that when lifting filter on upright position granulates will push flexible net and carbon bed become uneven—actually there will be holes on structures without any filter media. Airflows will go through those holes without filtration, thus there is no air flow resistance.
Electronic Air Cleaners:
Some air cleaners, such as externally powered electrostatic precipitators (also known as electronic air cleaners) have very often in the beginning high filtration efficiency. After charger unit there is collection section, which is normally steel plates or net.
Wire Corona Chargers:
Wire corona chargers are difficult to clean and on use they create ozone, even when they are clean.
Various air filters for supplying purified fresh air has been devised in a some of the measures are as follows:
CN2906423 relates to a natural fresh air into the home device outlet mainly used to connect to the wind in the outdoor side wall interior ventilation tube, three directions can be blown into the room. Disadvantage of this solution is that when temperatures and pressures in indoor and outdoor air are same or difference is only minimal then air from outdoor won't penetrate to indoor and carbon dioxide level will stay high.
CN203949307 relates to an air purifier, especially relates to a filter to clean indoor and outdoor air and aromatherapy function of air purification system. It further relates to a unit comprising pre-filter, PCO-filter, HEPA-filter, fan, activated carbon filter, formaldehyde filter, and ionizer inside smaller intake pipe that is located inside fresh air pipe. Disadvantage in this solution is that filter like HEPA and activated carbon filter causes high pressure drop and small size fan, like in this application can hardly overcome that.
Known prior arts CN203068671, CN10387928, CN293478450, CN2348284, CN203349399, CN203132030, CN201283117 and CN203704238 relates to filter, heat, cool and dehumidify or humidify fresh air from outdoor. Disadvantage of these solutions and air arrangement is that they need relatively big space and effective fans thus energy consumption and sound level are high. These solutions are converted as miniature models from Air Handling Units, old technology that has already been adapted and used globally, in HVAC industry, having only minor changes for last decades.
CN203421792 is intended to provide a type household air purification devices, it can effectively reduce interior noise in the room at the same time add fresh outdoor air, but this type of arrangements is that based on temperature difference, its hard to control amount of fresh air.
CN201277666 relates to a kind of air conditioning units, in particular, it relates to an outdoor fresh air into the indoor air conditioner, more particularly it relates to sleeve that is used for enabling connection of fresh air intake pipe and indoor located air purifier.
CN202442444 discloses that fresh air intake pipe and indoor located air purifier is connected with climb and climbing buckle.
Self-locking hung air purifier disclosed in CN4844749(Y) describes about the use of air intake pipe for permanent hanging solution.
Another known prior arts CN203443015(U), CN203980487U, CN103398441A, CN203642412(U), CN201069227, CN103644613, CN202590559, CN201253368, CN2199470(Y) discloses air purifier with rear shell excluding pipe connection that connects fresh air inlet.
Further known Prior arts CN103353153A, CN203097659(U), KR 100797894(81), CN2367950(Y) discloses the fresh air purifying unit that is mounted to windows.
CN203928174 relates to an air purification device, in particular a fresh air purifier that is design to suck fresh air from outdoor through small hole by using small air hose.
Yet another known prior arts CN103623665(A), CN103623665(A), CN203657089(U) discloses a fresh air purifying unit that is connected with hose to fresh air intake pipe and the said units are either firmly mounted to walls or removable unit on floors, like.
Another known prior arts CN203731589U, CN102563767B, CN201253367Y discloses mix fresh air with indoor air inside air purifier or air handling unit by using either manual or electrical driven mechanical valves or dampers.
Further known prior arts US201310213414A1, WO2010131031 (A2) relates to low pressure one way air valve in a flapper disc type.
Another known prior art of passive electrostatic air filters EP1596960(B1), KR20110008369(A), KR101317615(B1) relates to electrostatic charges, that may be either natural or imposed upon the media during manufacturing. For enabling air through tightly formed filter media structures, plurality of protrusions is formed on an electrified film. The disadvantages of these inventions are that such filters may demonstrate high efficiency while considering their use (with low air velocity) and drop rapidly in efficiency during their actual life cycle. One of the main reasons is that ultrafine and fine particles will cover charged fibers or charged film that finally switch of its magnetic field. Due these solutions weak electric field, filtration efficiency of fine particles will decrease significantly, when air velocity inside filter media increases. To avoid this dramatic drop of filtration efficiency, protrusions are irregularly formed on an electrified film with very narrow cap between filter film layers. This leads uneven distribution of dust inside filter media and only the front surface of the filter will be loaded with dust that logs filter.
Yet another U.S. Pat. No. 5,993,521A relates to two-stage electrostatic filter where steel plates are replaced with non-metallic materials. When loading with dust, removal efficiency will decrease (plate-type) and/or pressure drop (Pa) will increase (net-type). Efficiency of these devices may decline over time, and their service life is dependent on the conductivity and the dust collected.
The present invention overcomes the inadequacies of the prior art by providing air filters that is easily installable and serviceable, that has environmentally friendly biodegradable disposable filters.